An American caregiver exposed to the Ebola virus while caring for a patient in Africa was given the new experimental vaccine within 24 hours and subsequently did not develop infection. As is often the case with diseases calling for post-exposure prophylaxis, it cannot be determined whether the vaccine prevented infection or whether the patient would not have developed Ebola regardless.
“We will never know whether that was the critical factor or whether he was just lucky and if his exposure was not intense enough [to seroconvert],” says Ted Cieslak, MD, infectious diseases specialist with Nebraska Medicine in Omaha.
The American missionary was exposed while providing care for an Ebola patient infected during the ongoing outbreak in the Democratic Republic of Congo. The vaccine has been deployed there, and the caregiver was immunized within 24 hours of the exposure, Cieslak says.
“We think the vaccine is good for the first few days post exposure,” he explains. “That’s different from other vaccines; for example, measles. If you were exposed to measles and you had not been vaccinated, it’s probably too late vaccinate at that point. With Ebola, we think there is a window of a few days there.”
After the exposure, the caregiver was flown out of Africa and quarantined in a state-of-the-art facility for the requisite three weeks at the Nebraska Medical Center, says Cieslak, who oversaw the case. The patient arrived for quarantine and monitoring at the medical center on Dec. 29, 2018. If he had developed Ebola, the plan was to transfer care to the nearby Nebraska Biocontainment Unit, where three infected healthcare workers were treated during the 2014 outbreak in West Africa.
As of Jan. 29, 2019, the Ebola outbreak in Congo included 752 cases, with 698 confirmed and 54 probable. The outbreak, which began in August 2018, has killed 465 people for a case-fatality rate of 62%, the World Health Organization reports.1
In some areas, there have been “nosocomial transmission events in private and public health centres” including patients, visitors, and healthcare workers, the WHO reported. Overall, 65 healthcare workers have been infected while caring for Ebola patients during the outbreak. At least 18 healthcare workers have died, but that number is based on an earlier report that included only 54 healthcare workers.
“In DRC, more than 66,000 people have been vaccinated — more than 21,000 of them are health and other frontline workers,” the WHO reports. “The yet-to-be-licensed rVSV-ZEBOV vaccine has been shown to be highly protective against the Zaire strain of the Ebola virus in a major trial.”2
The WHO did not clarify in the reports whether the healthcare workers who became infected and those who died had received the vaccine. However, healthcare workers in neighboring nations are being offered the vaccine, although no Ebola cases have appeared beyond Congo, the WHO reports.
A request to clarify the number of infected healthcare workers who were immunized had yielded no WHO response as this story was filed. In one of its outbreak reports, the WHO listed immunization of providers as one of the areas being strengthened.
“Health protection and control measures such as infection prevention and control in health centers, vaccination for healthcare and other frontline workers, and safe and dignified burial practices are being strengthened to interrupt the chains of transmission,” the WHO stated.3
Vaccine Efficacy, Quarantine Measures
Cieslak worked many years on biological countermeasures in the U.S. Army Medical Research Institute of Infectious Diseases in Fort Detrick, MD. He commented further on Ebola and the quarantine case in the following interview with Hospital Infection Control & Prevention.
HIC: Can you tell us more about the experimental Ebola vaccine?
Cieslak: This vaccine underwent a trial in Guinea during the 2014-2016 outbreak. It was a ring vaccination trial of high-risk individuals. For example, if somebody in a family died of Ebola, they immunized a ring around that person — all the close contacts. These are very high-risk patients who have been in [close] contact with someone who has Ebola. They did this ring vaccination trial, and it was 100% efficacious. There has been some criticism of that trial — it wasn’t big enough, etc. I’m sure more studies need to be done before the U.S. Food and Drug Administration would be willing to license that vaccine. Certainly, the preliminary data look very promising.
HIC: Just to clarify, this quarantined person had cared for patients in the ongoing outbreak in the Democratic Republic of Congo?
Cieslak: He was a healthcare provider. He cared for a patient who ultimately proved to have Ebola. At the time, they considered it a high-risk exposure. It occurred in the midst of some political unrest, and there were concerns. He was vaccinated post-exposure, as were all the of the Congolese healthcare providers who were on the team that cared for this patient. There are these concerns about any perceptions that the American or Western providers may get [the vaccine] and it is not as available to the Congolese. I think that has led to some [care units] not giving it until there is an exposure or there is high risk in their particular province.
HIC: What isolation measures did you use in caring for this patient?
Cieslak: We don’t actually call them patients. Technically, they are not admitted to the hospital. We usually refer to them as a “person under quarantine.” These are people who have been exposed to a potentially hazardous disease but have not yet come down with symptoms. The setting in our quarantine unit I would describe as more like a hotel. It is located on the medical center campus, but it is more like a hotel than a hospital.
The precautions we took in his case were fairly minimal. There are a few diseases — influenza, for example — where you actually can be contagious before you are symptomatic. With most diseases, including Ebola, you can’t transmit to others until you have symptoms. Given that this person was clinically well, we didn’t need to take too many precautions. He was kept on the quarantine unit so the general public did not have access to him, and he could not have visitors. The number of hospital personnel [entering the quarantine area] was limited to those who needed to interact with him.
HIC: You note that quarantine can be mandated, but in this case, it was voluntary.
Cieslak: The country issues what they call a voluntary quarantine agreement, and he signs that and agrees to abide by that. He was very cooperative, and there were no issues. Under the terms of the agreement, providers were supposed to remain three feet away from him unless they were wearing gloves and mask. I would postulate that is an abundance of caution. It’s technically not necessary, since again he was incapable of transmitting [Ebola] since he was not symptomatic.
HIC: What symptoms did you look for? Fever?
Cieslak: Fever is typically the first sign of Ebola. We took his temperature a few times a day. Other than that, it was subjective. We asked him to report any symptoms he was having and general questions about his health. The only vital sign we measured was temperature.
HIC: Why was the decision made to place this patient under quarantine at your facility? One would be the ease of transferring over to your biocontainment unit if symptoms developed?
Cieslak: Exactly. I think that’s why the state department and the CDC wanted him to come to our place. There were multiple factors in play.
In theory, a person like him, if you trust them, which we certainly did, and they have a place to go to, then they can be quarantined at home. They are just told to take their temperature a couple of times a day and call in if they develop a fever. He was a missionary in Africa and did not have a permanent home here in the states. That was part of the issue.
The assistant secretary for preparedness awarded us this grant to build a better quarantine facility, so I think there was an element of testing the system and seeing how it worked. But again, he really had no place to go to.
His organization and our state department thought the better part of valor was to get him out of Africa and bring him here.
- WHO. Ebola virus disease – Democratic Republic of the Congo. Update: Jan. 24, 2019. Available at: https://bit.ly/2BlTjBX.
- WHO. South Sudan vaccinates health workers against Ebola. Jan. 28, 2019. Available at: https://bit.ly/2GssX4u.
- WHO. Ebola virus disease – Democratic Republic of the Congo: Update: Jan. 31, 2019. Available at: https://bit.ly/2SvYitE.
